1. Field of the Invention
This invention relates to a belt type continuously variable transmission system for use in a vehicle such as a motor vehicle (hereinafter, "continuously variable transmission" being referred to briefly as "CVT").
2. Description of the Prior Art
As a transmission in a vehicle such as motor vehicle, there has recently been proposed a belt type CVT system (refer to Japanese Patent Application No. 144985/1983 for example).
For example, the belt type CVT system of this type comprises:
a fluid coupling device for transmitting an output from an engine by use of fluid;
a belt type CVT device for transmitting an output from the fluid coupling device at a transmission gear ratio of the continuous variation through a belt;
an anxiliary transmission device having a function of shifting an output from the belt type CVT device in accordance with the forward or backward running conditions;
a reduction gear device for reducing an output from the auxiliary transmission device;
an oil pump device for feeding the hydraulic pressures to a valve body and other various hydraulic components, and so forth.
In the belt type CVT device, an input pulley and an output pulley each having a circumferential groove of a V-shape in cross section are provided on a first and second rotary shaft, respectively, and a transmission belt is racked across the input pulley and the output pulley, being guided around the circumferential grooves of the both pulleys, respectively. The widths of the circumferential grooves of V-shape in cross section of the input and output pulleys are varied relative to each other, and a rotational force is transmitted from one rotary shaft to the other, being continuously variable.
With this belt type CVT device, it is possible to make a shift only in one rotational direction, and a shift in a reverse direction, namely, a shift from forward to reverse running cannot be performed. Because of this, in order to use this as a transmission in a vehicle such as a motor vehicle, an auxiliary transmission device having a forward-reverse shift transmission mechanism is provided on the belt type CVT device. The auxiliary transmission device is disposed on the rotary shaft of the pulley either the input side or the output side of the belt type CVT device. Since the belt type CVT system can be made compact in size, there have recently been many proposals in which the auxiliary transmission device is disposed at the output side. Furthermore, the auxiliary transmission device is provided thereon with a forward transmission mechanism of double reduction or so in the forward-reverse shift mechanism.
Because of this, in many cases, the auxiliary transmission device is formed by use of a planetary gear device, which has a clutch device and a braking device. The clutch device and the braking device of a friction multi-plate engaging type in many cases, and operated by hydraulic pressures. Each of the clutch device and the braking device include a well-known hydraulic pressure servo device, and speed change can be obtained by selectively operating the clutch device and the braking device.
As well known, the planetary gear device is constituted by elements including a sun gear, planetary gears rotatably supported by carriers and a ring gear. The clutch device is connected to one of the aforesaid elements of the planetary gear device through a flange member on a disc, whereby the power transmission is performed. As one of these power transmitting arrangement, there is provided an arrangement wherein the flange member is connected to the sun gear of the planetary gear device.
Additionally, due to meshing engagement with the planetary gears, the sun gear normally generates a thrust force, and a thrust bearing to receive this thrust force is provided at a position on one side of the sun gear.
Furthermore, the carriers for rotatably supporting the planetary gears are disposed at positions opposite each other in the axial direction of the planetary gears. As a consequence, the carrier is disposed on the side, where the flange member connecting the clutch device to the sun gear is provided, at a position adjacent the flange member.
On the other hand, the braking device in the auxiliary transmission device is provided for fixing these elements of the planetary gear device to a case member. To fix the ring gear to the case member, the braking device is interposed between the ring gear and the case member. In general, the braking device is of a friction multi-plate engaging type which is well known, in many cases, and a frictionally engageable member is pushed by a piston driven by hydraulic pressure, so that the ring gear is fixed to the case member. This piston is adapted to be coupled to a cylinder member for the operation, and, when the cylinder member is formed separately of the case member, the cylinder member is engaged with the case member in the axial direction through a cover ring. A thrust force of the cylinder member generated as a reaction force due to the working of the piston is received by the case member through the cover ring. It is further noted that the thrust force generated in the cylinder member is about 2 tons in value.
The ring gear of the planetary gear device is in meshing engagement with the planetary gears, and, since this meshing engagement is normally a helical meshing engagement, a thrust force is generated in the ring gear due to the meshing engagement. Conventionally, the thrust force generated in the ring gear is received by a case member, being different from the thrust force of a cylindrical member of the braking device. In passing, the thrust force generated in the ring gear is about 400 Kg in value, which is smaller in value than the thrust force generated in the cylindrical member.
When the belt type CVT device and the auxiliary transmission device are provided in the transmission system, the former together with the latter are normally housed and installed in one chamber formed by a case member. Since these two members are housed together, in many cases, power transmissions are integrally connected to each other in the former and the latter. Furthermore, a power transmission between these two components and another device may be integrally formed similarly to the above. More specifically, for example, a component part of the auxiliary transmission device is integrally mounted to a rotary shaft of the output pulley of the belt type CVT device, whereby the belt type CVT device and the auxiliary transmission device cannot be separated from each other.
Furthermore, a partition member may be provided between the auxiliary transmission device and the belt type CVT device to divide the two from each other. When this partition member is provided, the rotary shafts of the belt type CVT device are supported on this partition member through bearings. Various oil lines are formed in the partition member disposed as per the above-described position. For example, there is formed an oil line for feeding the hydraulic pressure to the clutch device of the auxiliary transmission device, which clutch is of the friction multi-plate engaging type. Additionally, there is provided an oil line for feeding the controlling hydraulic pressure to a hydraulic cylinder device of the belt type CVT device in communication with an oil line formed in the rotary shafts. Furthermore, a seal member for sealing oil lines is provided at a connecting portion where the oil lines formed in the partition member and the oil lines formed in the rotary shafts are interconnected.
Now, due to a requirement concerning the positional arrangement, the auxiliary transmission device may be provided at a position in the upper portion of a transmission system, being spaced apart from the position of oil located in the lower portion of the transmission system. For example, when the auxiliary transmission device is disposed at the output side of the belt type CVT device, since the oil pump is provided at the input side and disposed at a lower position close to the position of the oil pool, the output pulley, and the auxiliary transmission device are located at position located upward from a differential gear device and the like, whereby the auxiliary transmission device is provided in the upper portion of the transmission system.
Furthermore, the transmission system is provided with a hydraulic control device, to control the working of a hydraulic servo device of the auxiliary transmission device, to control the pulleys of the belt type CVT device, and further, to control a fluid coupling and a lock-up clutch when the transmission system includes the fluid coupling device with the lock-up clutch. The hydraulic control device is provided thereon with various valves including a pressure regulator value such as the pressure regulator valve for regulating the supplied hydraulic pressure and the like, and a shift valve for controlling the working of the hydraulic servo device of the auxiliary transmission device. These various valves are assembled into a valve body.
The valve body has been commonly provided in the lower portion of the transmission system and close to the oil pool. This is because it is preferable that the hydraulic pressure pumped up by an oil pump be regulated in pressure as soon as possible. However, the hydraulic servo device of the auxiliary transmission device is spaced apart from the valve body.
On the other hand, in general, to improve the transmission gear ratio obtainable from the belt type CVT device, the belt type CVT system is provided with a reduction gear device in addition to the aforesaid auxiliary transmission device. The reduction gear device is formed of an ordinary gear device wherein large and small gears different in diameter from one another are in meshing engagement with one another. This reduction gear device is commonly disposed on the output side of the belt type CVT device. Since the auxiliary transmission device is disposed on the output side immediately after the belt type CVT device, the reduction gear device is disposed on the downstream side of the auxiliary transmission device.
One of the rotary shafts of gears of the reduction gear device is provided coaxially with the rotary shaft of the output pulley of the belt type CVT device, and this rotary shaft of the reduction gear device is rotatably and integrally connected thereto with an output member, such as for example the carrier of the planetary gear device constituting the auxiliary reduction gear, whereby the power is transmitted from the auxiliary transmission device to the reduction gear device. In this case, commonly, the output member such as the carrier of the planetary gear device is inseparably and integrally formed with the rotary shaft of the reduction gear device in the axial direction, too.
Now, even in the case of a motor vehicle having a size of that of a common passenger vehicle in general, a load as high as 500 Kg or more acts on the transmission belt racked across the input pulley and the output pulley in the belt type CVT device during the transmission of the power, whereby a high load corresponding thereto acts on the input pulley and the output pulley, which are subjected to the load of this transmission belt.
On the other hand, the input pulley and the output pulley are rotatably supported by case members of the transmission system and the support thereof is effected by the support of rotary shafts of stationary pulleys. One end of the rotary shaft is directly supported by the case member of the transmission system through a bearing. Since, in general, other devices such as the auxiliary transmission device are provided on the other end of the rotary shaft as aforesaid, the other end of the rotary shaft is supported through a member or members of these other devices. Because of this, the supporting distance between opposite ends of the input pulley and the output pulley becomes relatively long, whereby the rigidity feature becomes low and the supporting accuracy is lowered because the rotary shaft is supported through the member or members of the aforesaid other devices.
As a result, since the conventional input and output pulleys are low in terms of supporting accuracy, deviations may occur from preset positions of the provision of the input and the output pulley, whereby the transmission belt may move in a zigzag fashion between the input pulley and the output pulley. Here, the deviations from the preset positions of the provision means deviations in position from the axes of the rotary shafts of the pulleys and the deviations in position in the axial direction of the rotary shafts.
When the input pulley and the output pulley are subjected to a high load during the transmission of the power as described above, since the supporting distance therebetween is long and the rigidity is low, a flexible deformation occurs in a direction of mutual approach, whereby a deviation may occur too. This deviation is added to the deviation from the aforesaid supporting accuracy, whereby the deviations at the positions of the provision of the input pulley and the output pulley are further increased, with the result that the transmission belt moves in a zigzag fashion to a further extent.
In general, the transmission belt is constituted by an endless carrier formed by laminating thin metallic hoops and power transmission metallic blocks, and a plurality of the power transmitting blocks are provided on the endless carrier in a manner to be tied in a row. When the thus formed transmission belt moves in a zigzag fashion, the hoops forming the endless carrier move in the lateral direction relative to the power transmitting blocks, end faces of the hoops abut against abutment portions of the power transmitting blocks, whereby the transmission belt suffers from fatigue, thus possibly presenting the disadvantage of lowered durability of the transmission belt.
Further, if the power transmission connection between the belt type CVT device and the auxiliary transmission device and between the above-mentioned components and another device are made integral and inseparable from each other, even when one of the belt type CVT device and the auxiliary transmission device is subjected to a replacement of parts or repair, the other device should be disassembled and assembled, thus presenting the disadvantage of undergoing troublesome replacement and repair.
Furthermore, when the hydraulic servo device of the auxiliary transmission device is spaced apart from the valve body, there may be presented the disadvantage that the transmission responsiveness of the auxiliary transmission device is low. This is because the operation hydraulic pressure is fed to the hydraulic servo device of the auxiliary transmission device through a valve such as a shift valve for controlling working of the auxiliary transmission device, which valve is provided in the valve body, and, in this case the working hydraulic pressure is fed through an orifice formed in an oil line disposed close to the valve. Because of this, when the valve body is spaced apart from the auxiliary transmission device, the distance from the orifice to the hydraulic servo device becomes long, thus possibly presenting the disadvantage that the shift responsiveness becomes low through the action of the orifice.
Further, when, in the transmission system provided with the belt type CVT device and the auxiliary transmission device, the partition member is interposed between the belt type CVT device and the auxiliary transmission device, and this partition member is provided therein with the bearings for supporting the rotary shafts of the pulleys and the oil lines for feeding the hydraulic pressure to the auxiliary transmission device and the belt type CVT device, there may be presented such disadvantages that sealing properties of the seal members provided at oil line connections between the oil lines formed in the partition member and the oil lines formed in the rotary shafts are worsened and the clutch device of the friction multi-plate engaging type is increased in the diametral direction thereof, depending upon the positions where the bearings are provided.
For example, when the positions where the bearings for supporting the rotary shafts of the pulleys are provided are located rather to the side of the auxiliary transmission device than the positions of the various oil lines formed in the partition member, the oil lines connecting portion between the oil lines formed in the partition member and the oil lines formed in the rotary shafts is located rather to the belt type CVT device than the positions of the bearings. In this case, the rotary shaft portion located rather to the belt type CVT device than the bearings, is subjected to flexible deformation of the pulleys due to the load of the transmission belt, whereby premature wear is generated on the seal member provided in the aforesaid oil line connecting portion, thus presenting the disadvantage of lowered sealing properties in the oil line connecting portion.
Furthermore, when the bearings are located at the above-mentioned positions, the oil lines leading to the clutch device are located at positions radially outwardly of the positions of the bearings, and the clutch device is further radially outwardly located, thus presenting the disadvantage that the clutch device is increased in the diametral direction thereof.
Further, when the cylinder member of the braking device is formed separately of the case member and engaged with the case member in the axial direction by the cover ring, the thrust force generated in the cylinder member is received by the case member through the cover ring. However, the thrust force generated in the cylinder member is generally large, whereby the cover ring suffers from fatigue prematurely, thus presenting the disadvantage that the braking device durability is lowered. Heretofore, the thrust force generated in the ring gear of the planetary gear device has been received directly by the case member unlike the thrust force of the cylinder member of the braking device. However, the construction, wherein the thrust force is received by this case member, may present the disadvantage that the construction is complicated because the ring gear and the braking device are disposed close to each other.
Furthermore, when, in the transmission system provided with the belt type CVT device and the auxiliary transmission device, the clutch device and the braking device are formed into friction multi-plate engaging types, the friction multi-plate engaging type requires a relatively large space. Hence, when the above-described transmission system is combined with the planetary gear device, the resultant transmission system becomes relatively large-sized.
The inlet pulley and the outlet pulley of the belt type CVT device are controlled by the hydraulic cylinder devices which are large-sized devices requiring relatively large spaces. In many cases, the hydraulic cylinder device for the inlet pulley and the auxiliary transmission device are disposed at positions interfering with each other. Because of this, the positional arrangement of the both devices constitutes one of the important factors in making the transmission system compact in size. Heretofore, the necessity has been voiced for making the transmission system mounted on a vehicle such as a motor vehicle as compact as possible. Particularly, there has been a strong requirement for making the transmission system compact in a front engine-front device (F--F) motor vehicle. Since there is a restriction imposed on the vehicle width in the F--F vehicle wherein an engine is mounted transversely, it has been difficult to realize it.
Additionally, the factors in making the transmission system of this type compact in size are constituted by decreasing the distance across the rotary shafts of the inlet and outlet pulleys to be as short as possible and making the axial length in the auxiliary transmission device as short as possible.
Further, when the clutch device and the sun gear of the planetary gear device are connected to each other through the flange member, if the flange member is connected to the sun gear under an ordinary arrangement, then there is presented the disadvantage that the axial length of the device becomes long. More specifically, in the case of connection under the ordinary arrangement, the carrier disposed on the side of the flange member, the flange member and a thrust bearing subjected to a thrust force of the sun gear are simply arranged in the axial direction, whereby the appropriate axial lengths of the above-described three elements are required for the arrangement of the device, thus presenting the disadvantage that the axial length becomes relatively long.
Furthermore, when the power transmission connection between the auxiliary transmission device and the reduction gear device is made integrally and inseparably in the axial direction, if the replacement of parts and repair are performed in the reduction gear device, then an adverse influence effect occurs on the auxiliary transmission device, whereby the auxiliary transmission device should also be disassembled and assembled, thus presenting the disadvantage of undergoing troublesome replacement of parts and repair. Furthermore, lubrication is required at lubricating portions such as bearing portions of the auxiliary transmission device, which are provided on the rotary shaft of the output pulley. Because of this, the provision of lubrication paths is required, however, since the auxiliary transmission device is interposed between the belt type CVT device and the reduction gear device, thus presenting the disadvantage that it is difficult to provide the lubricating paths.
Further, in general, the transmission system is provided with an oil pump device for feeding the hydraulic pressure to various hydraulic components such as a valve body. When this oil pump device is provided on a system of power transmission of the inlet pulley of the belt type CVT device, e.g. at a downstream position, a shaft for driving the oil pump device should be extended through the rotary shaft, thus presenting the disadvantage that the positional arrangement thereof becomes complicated.